Optical devices used in communications applications often have a light-transmitting medium positioned on a base. Optical gratings for separating light signals of different wavelengths are often formed in the light-transmitting medium. Waveguides for guiding the light signals can also be defined in the light-transmitting medium. The light-transmitting medium generally includes a free propagation region between the waveguides and the optical grating.
During operation of these optical devices, a portion of the waveguides carry the light signals to the free propagation region of the light-transmitting medium. The light signals travel through the free propagation region to the optical grating. The optical grating includes a reflecting surface that reflects the received light signals back into the free propagation region. The light signals are reflected such that the light signals of different wavelengths separate as they travel through the free propagation region. Another portion of the waveguides receive the separated light signals from the free propagation region and carry the separated light signals away from the optical grating.
These optical gratings are associated with an undesirably high level of optical loss. As a result, there is a need for improved optical gratings.